Gas generator

ABSTRACT

A gas generator in the form of a self-starting two cycle free piston internal combustion engine which generates hot exhaust gases and steam as required by the load. A reciprocating piston assembly comprised of three-coupled pistons compresses air in a combustion cylinder to the point of fuel ignition, pumps scavenging air, and compresses and stores a volume of air for recycling the generator. A novel valve arrangement responsive to gas consumption activates the cycling of the piston assembly.

United States Patent [72] Inventor James S. Carter 1937 Grace Ave. Apt.#4, Hollywood, Calif. 90028 [21] Appl. No. 878,787

[22] Filed Nov. 21, 1969 [45] Patented Oct. 5, 1971 [54] GAS GENERATOR13 Claims, 4 Drawing Figs.

52 US. Cl 123/46 R, 60/13,123/46 SC [51] lnt.Cl F02b 71/00 [50] Field ofSearch 123/46 R,

46 SC, 46 B; 60/13 [56] References Cited UNITED STATES PATENTS 2,462,7452/1949 Horgen... 123/46 2,849,995 9/1958 Lewis 123/46 2,933,884 4/1960Foster 60/13 F 3,024,591 3/1962 Ehrat et al. 123/46 X 3,188,805 6/1965Gahagen 123/46 X 3,314,403 4/1967 Bouvier et al...; 123/46 FOREIGNPATENTS 840,047 7/1960 Great Britain 123/46 754,168 9/1952 Germany123/46 Primary ExaminerWendell E. Burns Att0rneySpensley, Horn & LubitzABSTRACT: A gas generator in the form of a self-starting two cycle freepiston internal combustion engine which generates hot exhaust gases andsteam as required by the load. A reciprocating piston assembly comprisedof three-coupled pistons compresses air in a combustion cylinder to thepoint of fuel ignition, pumps scavenging air, and compresses and storesa volume of air for recycling the generator. A novel valve arrangementresponsive to gas consumption activates the cycling of the pistonassembly.

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BY M% GAS GENERATOR BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to generator of power gas and, moreparticularly, to a self-starting free piston reciprocating engine inwhich a mixture of steam and power gas is produced by the combustion offuel.

2. Prior Art Hot compressed gas, hereinafter referred to as power gas,is commonly used to power such devices as gas turbines and steamengines. One common method of generating power gas is by the combustionof fuel in an internal combustion engine.

The exhaust gases of the engine are piped to the gas turbine or otherload instead of being allowed to escape to atmosphere as is done withmechanically loaded internal combustion engines.

Some loads are relatively constant, that is, exhibit a constant or onlymoderately varying rate of power gas consumption. Gas generatorsdisclosed by the prior art can be designed to satisfactorily supply therelatively constant demand of this type load.

Other loads present widely fluctuating requirements for power gas to thegenerator. Such demands have heretofore been very difficult to supplysince the speed range of internal combustion engines is limited. Forexample, when the demand falls to a small fraction of full output or tozero for some period of time, the generators disclosed by the prior artmust be stopped and restarted on some schedule depending on the loadrequirements or if left running continually must have their outputstored or vented to the atmosphere. Such procedures are bothersome,expensive and wasteful.

The present invention overcomes this problem by utilizing a novel valvearrangement which makes each generator engine cycle independent of everyother engine cycle. Engine speed, that is, the number of cycles per unittime is dependent wholly on the requirements of the load since eachgenerator cycle is independently initiated based on the sensing of apredetermined quantity of power gas consumption. Thus, a smooth andautomatic accommodation to the load is made by the present inventionfrom zero consumption to full output. Each cycle of operation issubstantially identical to every other cycle in terms of duration, fuelconsumption, air consumption, etc. The net speed changes because of thechange in the number of cycles per unit time rather than the characterof the cycle itself.

Prior art gas generators do not have constant cycle characteristics butinstead achieve output variations by varying the character of the cycleitself as, for example, by varying the quantity of fuel injected percycle. Such methods result in richer fuel mixtures at some speedsettings than at others with the result that an excessive amount ofharmful smog producing pollutants is present in the power gas andeventually may find its way to the atmosphere. This invention, becauseof its constant cycle characteristics, can be set for most completecombustion (minimum pollutants) at all rates of consumption.

SUMMARY OF THE INVENTION The present invention is basically a two-cycleinternal combustion engine in which the hot exhaust gases constitute theentire useable output. In accordance with the presently preferredembodiment of the invention, a piston assembly, comprised of threepistons, reciprocates in response to the demand of the load. Theassembly is propelled in one direction by the expansion of a burningfuel-air mixture and in the other by compressed air. The cycle isinitiated by the release of energy stored in the form of compressed air.The air, compressed and stored during the burning phase of a reviouscycle, is brought to bear on one of the pistons of the piston assemblythereby causing the piston assembly to move. Piston assembly motioncompresses the air contained in a combustion cylinder causing itstemperature to rise to a temperature sufficient to cause fuel ignition.Fuel is injected into the combustion cylinder after the compressionstroke, and due to the high temperature of compression, ignition takesplace driving the piston assembly back. The recycling air isrecompressed and returned to its storage chamber and is thus availablefor the next cycle. At the same time, a third piston compressesatmospheric air to be stored in a second storage chamber for use inscavenging the combustion cylinder.

So long as there is no demand for gas, the pressure in the combustionchamber remains relatively high and a master control valve prevents thestored air in the first chamber from initiating another cycle. Gasdemand reduces the pressure in the combustion cylinder and allowsscavenging air to enter the cylinder. Flow of scavenging air out of itsstorage chamber causes a reduction in scavenging air pressure which inturn causes the master control valve controlling the recycling air toopen, thus initiating a new cycle. This novel method of controlling therecycling air allows the generator to supply a wide range of gas demandextending from zero to the maximum capability of the unit, automaticallyadjusting to the load. Waste heat from the combustion cylinder isutilized to generate steam which is mixed with the exhaust gasesincreasing the net efficiency of the unit.

It is a primary object of this invention to provide a power gasgenerator which is self-starting.

Another object of this invention is to provide a power gas generatorwhich can efficiently supply power gas to steam engines and turbinesdesigned to operate over a wide range of speeds and loads.

Still another object of this invention is to provide a power gasgenerator in which the speed of operation is controlled by the demand ofthe steam engine or turbine being powered by it.

Still another object of this invention is to provide a power gasgenerator in which the heat of combustion conducted through the cylinderwalls of the combustion chamber is used to make steam which is mixedwith the power gas.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and advantages thereof will be better understoodfrom the following description considered in connection with theaccompanying drawings in which a presently preferred embodiment of theinvention is illustrated by way of example. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not intended as a definitionof the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section of a sideview of the presently preferred embodiment of the invention.

FIG. 2 is a cross section taken through plane 22 of FIG. 1.

FIG. 3 is a cross section taken through plane 33 of FIG. 1.

FIG. 4 is a cross section taken through plane 4-4 of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present inventionis comprised of three basic portions, a motor section, a scavenging airpump, and a recycling section.

Referring to FIG. 1, the motor section contains piston 13 disposedwithin combustion cylinder 3, check valve 5, passageways 4, and fuelinjection nozzle 19. The scavenging air pump is represented by piston17, cylinder I4, and check valves 24, 16, and 22. Finally, the recyclingsection comprises cylinder 11, piston 12, chamber 10, check valve 23.and master control valve 9.

Free piston gas generators disclosed in the prior art, such as theBouvier et al. US. Pat. No. 3,3l4,403, disclose the same generalsections as are in this invention, but as will hereinafter becomeevident, the novel arrangement of the recycling section and the improvedscavenging air pump leads to the substantial performance and otheradvantages of the present invention over the prior art as previouslydiscussed.

Power gas, ready for consumption, is stored in chamber 2 and, flows tothe load through conduit 34. Throttle 1 controls the flow. Passageways 4connect chamber 2 to the combustion cylinder 3 when piston 13 is in itslowest position, the quiescent state of the generator.

If, when the generator is in its quiescent state, throttle l is opened,stored power gas will flow from chamber 2 and cylinder 3 to supply theload and as a consequence the pressure therein will drop. When thepressure drops to below the pressure of the air contained in scavengingair reservoir 6 (a pressure which may, for example, be about 170 p.s.i.)check valves 5 open allowing scavenging air to enter combustion cylinder3. As gas continues to flow through conduit 34, the pressure continuesto drop until the pressure in chamber 8, connected to reservoir 6through pipe 7, falls from the above mentioned higher pressure to apredetermined value, for example 150 p.s.i. Master control valve 9 nowhas 150 p.s.i. on one side of its actuator 37 and the pressure inchamber on the other. Chamber 10 contains stored recycling air which, inthe example being used, is at 170 p.s.i. as is discussed later. Thegreater pressure in chamber 10 as compared to chamber 8 causes mastercontrol valve 9 to open. Recycling air pressure from chamber 10 appliedto piston 12 causes the piston assembly consisting of pistons 12, 17,and 13 to move upward compressing the air in combustion cylinder 3. Atthe same time air in chamber 14 is transferred to chamber 15 throughcheck valve 16.

As air in cylinder 3 is compressed it, of course, heats in accordancewith the well known gas laws and near the top of its travel, piston 17engages fuel injection control rod 18 causing fuel to be injected intocylinder 3 through fuel nozzle 19. Fuel, such as diesel fuel, from atank, not shown, is supplied through tube 20. Heat from the compressedgas ignites the fuel causing the pressure in cylinder 3 to increase andthe piston assembly to move downward.

Prior to combustion, when the piston is at the top of its travel,passageway 36 is uncovered allowing air in tube 7 to enter cylinder lland equalizing the pressure in chambers 8 and 10. The master controlvalve 9 then closes. As the piston assembly moves downward, air iscompressed in cylinder 11 and flows into chamber 10 through check valve23 until, at the bottom of the stroke, chamber 10 contains air at apressure depending on the geometry of the pistons, cylinders, andchambers. In the example being cited, this pressure is 170 p.s.i.

At the same time air in chamber 15 flows through check valve 22 and tube7 into chambers 6 and 8 replenishing the scavenging air supply, buildingits pressure back to 170 p.s.i.; this pressure also being a function ofthe geometry of the parts.

The prior art, such as Bouvier et al. U.S. Pat. No. 3,314,403 disclosesa single stage scavenging air pump compressing the scavenging air on thecompression stroke of the motor piston. The present invention, in thepreferred embodiment, uses a two stage scavenging air compressor whichpresents a lighter load to the recycling section since the major portionof scavenging air compression takes place on the power stroke ratherthan the compression stroke of the motor section piston.

When the passageways 4 are uncovered, burned gas flows into chamber 2and thence out through conduit 34.

When the pressure in chamber 2 falls due to gas flow through conduit 34,the cycle is repeated providing a continuous flow of gas as required. Ifthe throttle is closed removing the demand, the generator stopsautomatically, since the cycle is activated by a drop in pressure of thepower gas.

Master control valve 9, which has no counterpart in the prior art,prevents the recycling air stored in chamber 10 from acting on recyclingpiston 12 until sufficient power gas has been consumed by the load torequire replenishment.

When there is no demand and the unit remains idle for some time thesmall amount of gas which can leak past piston 13 is prevented fromentering chamber 14 by seals 30, 31 and 32. Any leakage past seals 30and 31 is exhausted to atmosphere through opening 33.

Water jacket 25 is filled with water through tube 28 to a leveldetermined by float valve 27. Heat from combustion in cylinder 3 causesthe water in jacket 25 to boil and when sufficient pressure is built upthe steam enters chamber 2 through check valve 26. If a source of highpressure water is not available, a small steam engine pump can be drivenfrom tube 29 to supply tube 28.

Initial startup of the generator may be accomplished by pressurizingchambers 2, 6 and 10 to, in the example cited, p.s.i. or to whatever isthe design quiescent scavenging air pressure of the particular unit,which may be more or less than 170 p.s.i. After initialpressurization,.opening of throttle 1 will initiate operation andmaintain the proper pressures as described.

For convenience, the invention has been described using a piston andcylinder as a force summing device, however, it will be evident to thoseskilled in the art that other force summing devices such as diaphragmsor bellows would be as suitable. Reference to pistons and cylindersherein should be understood, therefore, to include other force summingdevices.

What has been described is a novel and improved power gas generator. Thepreferred embodiment has been shown with a single piston assembly forconvenience and ease of presentation but it will be obvious to thoseskilled in the art that this invention lends itself to the configurationof two opposed piston assemblies, common in the free piston engine artas a vibration reducing measure. Various other modifications will beapparent to those skilled in the art and are considered to be within thespirit of this invention as set forth in the appended claims.

lclaim:

l. A gas generator comprising:

a. A combustion cylinder having inlet and exhaust ports;

b. means for introducing fuel into said combustion cylinder;

c. a first piston slidable within said combustion cylinder;

d. a scavenging air pump for supplying compressed air to said combustioncylinder;

e. a first air storage chamber in communication with said scavenging airpump and with said combustion cylinder for storing the compressed airprovided by said scavenging air pump;

f. a first valve controlling the flow of air between said first airstorage chamber and said combustion cylinder;

g. a second cylinder spaced from said combustion cylinder;

h. a second piston coupled to said first piston and positioned withinsaid second cylinder:

i. a second air storage chamber adapted to store air compressed by themotion of said second piston in said second cylinder wherebysubstantially all of the air from said second cylinder is stored in saidsecond air storage chamber during a portion of each cycle of operation;and

j. a second valve controlling the flow of air between said secondstorage chamber and said second piston, whereby actuation of said secondvalve allows compressed air from said second storage chamber to act onand move said second piston thereby causing said first piston tocompress the gas in said combustion cylinder.

2. A gas generator as defined in claim 1 wherein said second valve isresponsive to a drop in pressure in said first air storage chamber.

3. A gas generator comprising:

a. first, second and third concentric cylinders spaced axially;

b. first, second and third pistons slidable within said first, secondand third cylinders respectively, said pistons being coupled;

c. a first air storage chamber;

d. first and second check valves connecting said first and secondcylinders respectively to said first air storage chamber, whereby airmay flow from said second cylinder into said first air storage chamber,and from said first air storage chamber into said first cylinder;

e. a second air storage chamber;

f. a pressure responsive valve connecting said second air storagechamber with said third cylinder, said pressure responsive valve beingresponsive to the pressure in said first air storage chamber, wherebyair in said second air storage chamber is allowed to flow into saidthird cylinder when pressure in said first air storage chamber drops;

. a third check valve connecting said second air storage chamber withsaid third cylinder whereby air may flow from said third cylinder intosaid second air storage chamber;

h. a fourth check valve opening into said second cylinder allowing airfrom the atmosphere to enter said second cylinder;

. a fuel injector opening into said first cylinder, said fuel injectoroperating in response to motion of said pistons; and,

j. a gas output conduit connected to said first cylinder.

4. A gas generator as in claim 2 and further including a water jacketsurrounding said first cylinder, said water jacket communicating withsaid gas output conduit, whereby steam generated in said water jacketwill flow out through said gas output conduit.

5. In a free piston combustion gas generator:

a. a recycling air storage chamber;

b. a cylinder connected to said recycling air storage chamber;

c. a piston slidable in said cylinder for recycling the generator, saidpiston being attached to the combustion cylinder piston of the generatorsaid piston being positioned in said cylinder such that substantiallyall of the air from said cylinder is stored in said recycling airstorage chamber during some portion of each gas generator cycle; and

d. a valve controlling the flow ,of recycling air from said storagechamber to said cylinder whereby recycling air will be brought to bearon said piston upon actuation of said valve.

6. The combination as recited in claim 5 wherein said valve isresponsive to gas consumption.

7. A gas generator comprising:

a. a motor section, said motor section including a free piston;

b. a scavenging air pump coupled to said free piston; and,

c. a recycling section, said recycling section comprising:

i. a cylinder;

ii. a second piston slidable in said cylinder, said second piston andsaid cylinder defining a closed variable volume and said second pistonbeing coupled to said free piston;

iii. an air storage chamber communicating with the variable volumedefined by said cylinder and said second piston, said air storagechamber being proportioned with respect to said variable volume thatsubstantially all of the air from said variable volume is stored in saidair storage chamber during a portion of each gas generator cycle; and

iv. a valve controlling the flow of air between said air storage chamberand the variable volume defined by said cylinder and said second piston.

8. A gas generator as defined in claim 7 wherein said valve isresponsive to the pressure of air pumped by said scavenging air pump.

9. A gas generator as defined in claim 8 wherein said scavenging airpump is a two stage pump.

10. A gas generator comprising:

. a. a motor section, said motor section including a first force summingmeans;

b. a scavenging air pump coupled to said first force summing means; and,

c. a recycling section, said recycling section comprising:

i. second force summing means coupled to said first force summing means;

an air storage chamber; lll. means for allowing air In said air storagechamber to communicate with said force summing means said air storagechamber and said force summing means being so proportioned thatsubstantially all of the air bearing on said force summing means isstored in said air storage chamber during a portion of each gasgenerator cycle; and

iv. a valve controlling the flow of air between said air storage chamberand said force summing means.

11. A gas generator as in claim 10 wherein said valve is responsive tothe pressure of air pumped by said scavenging air pump.

12. A gas generator comprising:

a. A combustion cylinder having inlet and exhaust ports;

b. means for introducing fuel into said combustion cylinder;

c. a first piston slidable within said combustion cylinder;

d. a scavenging air pump for supplying compressed air to said combustioncylinder;

e. a first air storage chamber in communication with said scavenging airpump and with said combustion cylinder for storing the compressed airprovided by said scavenging air pump;

f. a first valve controlling the flow of air between said first airstorage chamber and said combustion cylinder;

g. a second cylinder spaced from said combustion cylinder;

h. a second piston coupled to said first piston and positioned withinsaid second cylinder;

i. a second air storage chamber adapted to store compressed air pumpedby said second piston;

j. a second valve controlling the flow of air between said secondstorage chamber and said second piston, whereby actuation of said secondvalve allows compressed air from said second storage chamber to act onand move said second piston thereby causing said first piston tocompress the gas in said combustion cylinder; and

k. means for actuating said second valve to start each gas generatorcycle.

13. A gas generator as defined in claim 12 wherein said means foractuating said second valve is responsive to a drop in pressure in saidfirst air storage chamber.

1. A gas generator comprising: a. A combustion cylinder having inlet andexhaust ports; b. means for introducing fuel into said combustioncylinder; c. a first piston slidable within said combustion cylinder; d.a scavenging air pump for supplying compressed air to said combustioncylinder; e. a first air storage chamber in communication with saidscavenging air pump and with said combustion cylinder for storing thecompressed air provided by said scavenging air pump; f. a first valvecontrolling the flow of air between said first air storage chamber andsaid combustion cylinder; g. a second cylinder spaced from saidcombustion cylinder; h. a second piston coupled to said first piston andpositioned within said second cylinder: i. a second air storage chamberadapted to store air compressed by the motion of said second piston insaid second cylinder whereby substantially all Of the air from saidsecond cylinder is stored in said second air storage chamber during aportion of each cycle of operation; and j. a second valve controllingthe flow of air between said second storage chamber and said secondpiston, whereby actuation of said second valve allows compressed airfrom said second storage chamber to act on and move said second pistonthereby causing said first piston to compress the gas in said combustioncylinder.
 2. A gas generator as defined in claim 1 wherein said secondvalve is responsive to a drop in pressure in said first air storagechamber.
 3. A gas generator comprising: a. first, second and thirdconcentric cylinders spaced axially; b. first, second and third pistonsslidable within said first, second and third cylinders respectively,said pistons being coupled; c. a first air storage chamber; d. first andsecond check valves connecting said first and second cylindersrespectively to said first air storage chamber, whereby air may flowfrom said second cylinder into said first air storage chamber, and fromsaid first air storage chamber into said first cylinder; e. a second airstorage chamber; f. a pressure responsive valve connecting said secondair storage chamber with said third cylinder, said pressure responsivevalve being responsive to the pressure in said first air storagechamber, whereby air in said second air storage chamber is allowed toflow into said third cylinder when pressure in said first air storagechamber drops; g. a third check valve connecting said second air storagechamber with said third cylinder whereby air may flow from said thirdcylinder into said second air storage chamber; h. a fourth check valveopening into said second cylinder allowing air from the atmosphere toenter said second cylinder; i. a fuel injector opening into said firstcylinder, said fuel injector operating in response to motion of saidpistons; and, j. a gas output conduit connected to said first cylinder.4. A gas generator as in claim 2 and further including a water jacketsurrounding said first cylinder, said water jacket communicating withsaid gas output conduit, whereby steam generated in said water jacketwill flow out through said gas output conduit.
 5. In a free pistoncombustion gas generator: a. a recycling air storage chamber; b. acylinder connected to said recycling air storage chamber; c. a pistonslidable in said cylinder for recycling the generator, said piston beingattached to the combustion cylinder piston of the generator said pistonbeing positioned in said cylinder such that substantially all of the airfrom said cylinder is stored in said recycling air storage chamberduring some portion of each gas generator cycle; and d. a valvecontrolling the flow of recycling air from said storage chamber to saidcylinder whereby recycling air will be brought to bear on said pistonupon actuation of said valve.
 6. The combination as recited in claim 5wherein said valve is responsive to gas consumption.
 7. A gas generatorcomprising: a. a motor section, said motor section including a freepiston; b. a scavenging air pump coupled to said free piston; and, c. arecycling section, said recycling section comprising: i. a cylinder; ii.a second piston slidable in said cylinder, said second piston and saidcylinder defining a closed variable volume and said second piston beingcoupled to said free piston; iii. an air storage chamber communicatingwith the variable volume defined by said cylinder and said secondpiston, said air storage chamber being proportioned with respect to saidvariable volume that substantially all of the air from said variablevolume is stored in said air storage chamber during a portion of eachgas generator cycle; and iv. a valve controlling the flow of air betweensaid air storage chamber and the variable volume defined by saidcylinder and said second piston.
 8. A gas generator as defined in claim7 wherein said valve is responsive to the pressure of air pumped by saidscavenging air pump.
 9. A gas generator as defined in claim 8 whereinsaid scavenging air pump is a two stage pump.
 10. A gas generatorcomprising: a. a motor section, said motor section including a firstforce summing means; b. a scavenging air pump coupled to said firstforce summing means; and, c. a recycling section, said recycling sectioncomprising: i. second force summing means coupled to said first forcesumming means; ii. an air storage chamber; iii. means for allowing airin said air storage chamber to communicate with said force summing meanssaid air storage chamber and said force summing means being soproportioned that substantially all of the air bearing on said forcesumming means is stored in said air storage chamber during a portion ofeach gas generator cycle; and iv. a valve controlling the flow of airbetween said air storage chamber and said force summing means.
 11. A gasgenerator as in claim 10 wherein said valve is responsive to thepressure of air pumped by said scavenging air pump.
 12. A gas generatorcomprising: a. A combustion cylinder having inlet and exhaust ports; b.means for introducing fuel into said combustion cylinder; c. a firstpiston slidable within said combustion cylinder; d. a scavenging airpump for supplying compressed air to said combustion cylinder; e. afirst air storage chamber in communication with said scavenging air pumpand with said combustion cylinder for storing the compressed airprovided by said scavenging air pump; f. a first valve controlling theflow of air between said first air storage chamber and said combustioncylinder; g. a second cylinder spaced from said combustion cylinder; h.a second piston coupled to said first piston and positioned within saidsecond cylinder; i. a second air storage chamber adapted to storecompressed air pumped by said second piston; j. a second valvecontrolling the flow of air between said second storage chamber and saidsecond piston, whereby actuation of said second valve allows compressedair from said second storage chamber to act on and move said secondpiston thereby causing said first piston to compress the gas in saidcombustion cylinder; and k. means for actuating said second valve tostart each gas generator cycle.
 13. A gas generator as defined in claim12 wherein said means for actuating said second valve is responsive to adrop in pressure in said first air storage chamber.